'Sherlock Holmes' epidemiologists track patients' histories

Outside the isolation ward of the COVID-19 designated hospital, Li Ruoxi, who barely finished putting on his protective gear, was soaked in sweat due to Beijing's summer heat wave.

Li, 33, has been an epidemiological investigator in the Fengtai district's center for disease control and prevention for seven years.

When an epidemic occurs, they trace the activities of confirmed cases in the shortest amount of time, analyze the infection route and transmission chain and take timely measures to stop the spread of the virus.

"We are the 'Sherlock Holmes' tracing the virus," Li said.

Since June 11, Beijing reported more than 300 confirmed locally-transmitted cases, most of which were in Fengtai. The detection of new cases has put pressure on Li and his colleagues.

Having finished his shift at 1 pm, Li received a message from a testing agency that a 3-year-old child had tested positive for COVID-19 and was transferred to the designated hospital for quarantine.

After reviewing the case's preliminary information through a phone call, Li packed protective equipment and sterilization supplies and drove his team to the hospital.

Yang Xiaoxing, who is head of the epidemiological investigation group of Fengtai's CDC, said the group consists of more than 70 members divided into small teams of three.

Upon entering the isolation ward, Li asked the child's mother a series of questions about their recent activities and contact history over the 14 days before the child tested positive.

He guided the mother to check her chat records on social messaging apps, mobile payment records and other details to help her recall what had transpired and where they had been.

"Our inquiries will cover specific details like the modes of transportation they used and even the type of face masks they were wearing when they came in contact with others," Li said.

During the one-hour investigation, Li and his colleague asked more than 50 questions through cross-examination and drew a preliminary conclusion that the child had a meal together with a relative who had been confirmed previously.

Thereafter, Li had to trace those close contacts, remind their communities to take preventive measures and complete the investigation report.

"Apart from asking questions and writing reports, we also provide humanitarian assistance," Yang said. "Some patients turn to us for help when they are in trouble. We will report their cases in a timely manner and help solve the problem."

A couple who had been diagnosed with COVID-19 had an unattended 1-year-old child. After receiving the message, Yang tried her best to help them resolve the issue. Eventually, the child tested positive, too.

"That's good news and bad news. At least the baby won't be separated from the mother," Yang said.

Since the nucleic acid sample is collected during the daytime, test results usually arrive at night. But no matter how late it is, as soon as a positive nucleic acid test is reported, these investigators will rush to the spot.

In their office, boxes of instant noodles and bottles of mineral water are piled up on the desk, with a foldable bed underneath. Some investigators who finished their overnight work crash on that bed, sometimes even without having a meal.

"We usually work more than 20 hours a day," Yang said.

In fact, owing to the efforts of these epidemiological investigators, the source of the epidemic in Beijing was identified within a very short period of time and response measures were immediately adopted to prevent the spread of the virus.

Li said this has been his busiest and most stressful period since he took this job, "but only if we trace the whereabouts of the virus in time can we make more people safe."